Chelsea's Champions League semi-final was always going to conjure up intrigue of one kind or another. There was the prospect of José Mourinho renewing his tête-à-tête with Pep Guardiola at Bayern Munich, or confronting his former employers Real Madrid to revisit all the rancour surrounding his departure from the Bernabéu last summer. And yet, in being paired with Atlético Madrid, the plot could hardly be thickened any further.

There are different strands to this tale. Most centre around Thibaut Courtois, the talented Belgium goalkeeper bought by Chelsea from Genk in 2011 who has yet to play for the club but is enjoying a third productive season on loan at Vicente Calderón. Uefa's statement on "competition integrity", released half an hour before the draw began, attempted to deliver some clarity on the matter. In Uefa's eyes, Courtois is available to play against his parent club.

A "private contract" between the clubs which might influence the other's team selection is "null, void and unenforceable so far as Uefa is concerned", while any attempt to enforce a clause would be "a clear violation" of its regulations and deserving of sanction.

Chelsea consider the details of the deal that took the 21-year-old to Spain to be private and confidential between player and clubs and have never admitted publicly to the existence of the clause, so there is frustration those details have been confirmed by the Atlético president, Enrique Cerezo. The financial obligation in question, amounting to €3m for each appearance against the Premier League side, is apparently beyond Atlético's means and would make his selection prohibitive which, according to Uefa, would constitute the influencing of the Spanish club's selection.

The governing body – albeit perhaps 24 hours too late – thrust the issue into the public domain, presumably to ward off the possibility of Courtois suddenly succumbing to a suspicious injury on the eve of the semi-final to fuel conspiracy theories. Yet, in reality, by going public it has most likely ensured any compromise agreement between the clubs is hushed up forever.

The reality is Chelsea rate Courtois. He has long been earmarked as the successor to Petr Cech at Stamford Bridge, his progress in Spain scrutinised on a weekly basis by the goalkeeping coach, Christophe Lollichon. "We liaise each week and I watch videos or go and see him," said the Frenchman, who had scouted the 17-year-old Courtois in Belgium eight or nine times to assess his ability. "For me, he is the next No1 in the world. He is exceptional. I never see this quality before, except [with] Petr.

"He is very intelligent, technically very good. Tactically he has to improve, and we work a lot with the video. I send him every week or every two weeks, depending on the schedule, my analysis of his games. I send him my answers. He is happy with the club he is at and with the level of competition. It is very difficult because Chelsea always need the best, so now we have to find the good timing [as to when he returns to his parent club]."

At some stage Lollichon and Mourinho will have to have an awkward conversation with Cech about succession, though that time is not yet. With that in mind, there has been some anxiety among the hierarchy at Chelsea that Courtois's contract will have only two years to run this summer. There have been talks with his representative and there will be further negotiations aimed at securing the goalkeeper to a new five-year deal.

The Belgian wants to play and would be deeply disappointed to miss out on the experience, which Chelsea also have to take into account. Atlético privately expect the player to commit his long-term future to Chelsea but, as soon as he signs, they will attempt to secure him for another season on loan.

To date, that arrangement has suited all parties. Chelsea paid around £7m to sign Courtois and they have seen his game develop rapidly in a fine side who have claimed the Europa League, played in the Champions League and become contenders for the Primera Liga during his time at the club. Furthermore, they have benefited financially from the temporary switches, the fees involved believed to be €1m in 2011, €2.75m in 2012 and €4.5m for this season. Those loan charges have effectively covered the cost of signing the youngster in the first place.

Atlético, beset by financial problems, have enjoyed having a world-class goalkeeper in their ranks whose permanent purchase, now at least, they could never have funded. Courtois has kept 21 clean sheets in 40 games, shipping 25 goals en route. They are desperate to retain him next term, so why strain relations with the club who own him?

The ace in Atlético's pack is Diego Costa. Chelsea covet the Brazil-born Spain striker and will make his signing this summer a priority as they seek to revamp their forward ranks. They may simply be confident that the colour of their money will persuade Cerezo to sell – Atlético need the cash – regardless of whether the clubs' relationship has broken down over Courtois' involvement in the Champions League semi-finals.

But would it not make more sense for them to waive the €6m fee that would be due if the Belgian participates in both games on the understanding that Costa will be made available to them this summer, and perhaps even for slightly less than the €38m being mooted in the Spanish capital?

There is a level of dialogue established between these teams, and those talks will continue until the first leg at Vicente Calderón. The likelihood is that Courtois will play in that fixture. It may not be until the summer, when the politics are played out, that true clarity reigns.